A steering apparatus for an automobile, as illustrated in FIG. 31, is constructed so that rotation of the steering wheel 1 is transmitted to an input shaft 3 of a steering gear unit 2, and as this input shaft 3 turns, the input shaft 3 pushes or pulls a pair of left and right tie rods 4, which apply a steering angle to the front wheels of the automobile. The steering wheel 1 is fastened to and supported by the rear end section of a steering shaft 5, and this steering shaft 5 is inserted in the axial direction through a cylindrical shaped steering column 6, and is supported by this steering column 6 such that it can rotate freely. The front end section of the steering shaft 5 is connected to the rear end section of an intermediate shaft 8 via a universal joint 7, and the front end section of this intermediate shaft 8 is connected to the input shaft 3 via a different universal joint 9. The intermediate shaft 8 is constructed so that the shaft can transmit torque, and can contract along its entire length due to an impact load, so that when the steering gear unit 2 is displaced in the backward direction due to a primary collision between an automobile and another automobile, that displacement is absorbed, which prevents the steering wheel 1 from displacing in the backward direction via the steering shaft 5 and hitting the body of the driver.
In this kind of steering apparatus for an automobile, in order to protect the body of the driver, this kind of steering apparatus for an automobile requires construction that that allows the steering wheel to displace in the forward direction while absorbing impact energy during a collision accident. In other words, after the primary collision in a collision accident, a secondary collision occurs when the body of the driver collides with the steering wheel 1. In order to protect the driver by lessening the impact applied to the body of the driver during this secondary collision, construction is known (refer to JP51-121929(U), JP2005-219641(A) and JP2000-6821(A)) and widely used in which an energy absorbing member, which absorbs an impact load by plastically deforming, is provided between the vehicle body and a member that supports the steering column 6 that supports the steering wheel 1 with respect to the vehicle body so that it can break away in the forward direction due to an impact load in the forward direction during a secondary collision, and displaces in the forward direction together with the steering column 6.
FIG. 32 to FIG. 34 illustrate an example of this kind of steering apparatus. A housing 10, which houses the reduction gear and the like of an electric power steering apparatus, is fastened to the front end section of a steering column 6a. A steering shaft 5a is supported on the inside of the steering column 6a such that it can only rotate freely, and a steering wheel 1 (see FIG. 31) can be fastened to the portion on the rear end section of this steering shaft 5a that protrudes from the opening on the rear end of the steering column 6a. The steering column 6a and the housing 10 are supported by a flat bracket on the vehicle side (not illustrated in the figure) that is fastened to the vehicle body so that they can break away in the forward direction due to an impact load in the forward direction.
To accomplish this, a bracket 12 on the column side that is supported in the middle section of the steering column 6a and a support bracket 13 on the housing side that is supported by the housing 10 are supported with respect to the vehicle body so that they both can break away in the forward direction due to an impact load in the forward direction. These support brackets 12, 13 both comprise installation plate sections 14a, 14b at one to two locations, and cutout sections 15a, 15b are formed in these installation plate sections 14a, 14b so that they are open on the rear end edges. With these cutout sections 15a, 15b covered, sliding plates 16a, 16b are assembled in the portions of the support brackets 12, 13 near both the left and right ends.
These sliding plates 16a, 16b are formed by bending thin metal plate such as carbon steel plate or stainless steel plate provided with a layer of a synthetic resin that slides easily, such as polyamide resin (nylon), polytetrafluoroethylene resin (PTFE) or the like on the surface into a U shape, having a top plate section and bottom plate section that are connected by connecting plate section. Through holes for inserting bolts or studs are formed in the top and bottom plates in portions that are aligned with each other. With these sliding plates 16a, 16b mounted on the installation plate sections 14a, 14b, the through holes are aligned with the cutout sections 15a, 15b that are formed in these installation plate sections 14a, 14b. 
The bracket 12 on the column side and the bracket 13 on the housing side are supported by the fastening bracket 11 on the vehicle side by screwing nuts onto bolts or studs that are inserted through the cutout sections 15a, 15b in the installation plate sections 14a, 14b and the through holes in the sliding plates 16a, 16b, and tightening the nuts. During a secondary collision, the bolts or studs come out from the cutout sections 15a, 15b together with the sliding plates 16a, 16b, which allows the steering column 6a and the housing 10 to displace in the forward direction together with the brackets 12 on the column side, the bracket 13 on the housing side and the steering wheel 1.
In the example in the figures, energy absorbing members 17 are provided between these bolts or studs and the bracket 12 on the column side. As this bracket 12 on the column side displaces in the forward direction, the energy absorbing members 17 plastically deform so as to absorb the impact energy that is transmitted to the bracket 12 on the column side by way of the steering shaft 5a and steering column 6a. 
As illustrated in FIG. 34, during a secondary collision, the bolts or studs come out from the cutout sections 15 am 15b allowing the bracket 12 on the column side to displace in the forward direction from the normal state illustrated in FIG. 33, and the steering column 6a displaces in the forward direction together with the bracket 12 on the column side. When this happens, the bracket 13 on the housing side as well breaks away from the vehicle body, allowing this bracket 13 on the housing side to displace in the forward direction. As the bracket 12 on the column side displaces in the forward direction, the energy absorbing members 17 plastically deform and absorb impact energy that is transmitted to the bracket 12 on the column side via the steering shaft 5a and the steering column 6a, lessening the impact applied to the body of the driver.
In the case of the construction illustrated in FIG. 32 to FIG. 34, the bracket 12 on the column side is supported by the bracket on the vehicle side at two locations, on both the right and left side, so that it can break away in the forward direction during a secondary collision. From the aspect of stable displacement in the forward direction without causing the steering wheel 1 to tilt, it is important during a secondary collision, that the pair of left and right support sections be disengaged at the same time. However, tuning in order that these support sections disengage at the same time is affected not only by resistance such as the friction resistance and the shear resistance to the disengagement of these support sections, but unbalance on the left and right of the inertial mass of the portion that displaces in the forward direction together with the steering column 6a, so takes time and trouble.
In order to stabilize the breaking away of the steering column in the forward direction during a secondary collision, applying the construction disclosed in JP51-121929(U) can be somewhat effective. FIG. 35 to FIG. 37 illustrate the construction disclosed in this document. In the case of this construction, a locking notch 18 is formed in the center section in the width direction of a bracket 11 that is fastened to and supported by the vehicle body and that does not displace in the forward direction even during a secondary collision, and this locking notch 18 is open on the edge of the front end of the bracket 11 on the vehicle side. Moreover, a bracket 12a on the column side is such that it is able to displace in the forward direction together with a steering column 6b during a secondary collision.
Furthermore, both the left and right end sections of a locking capsule 19 that is fastened to this bracket 12a on the column side is locked in the locking notch 18. In other words, locking grooves 20 that are formed on both the left and right side surfaces of the locking capsule 19 engage with the edges on the both the left and right sides of the locking notch 18. Therefore, the portions on both the left and right end sections of the locking capsule 19 that exist on the top side of the locking grooves 20 are positioned on the top side of bracket 11 on the vehicle side on both side sections of the locking notch 18. When the bracket 11 on the vehicle side and the locking capsule 19 are engaged by way of the locking grooves 20 and the edges on both sides of the locking notch 18, locking pins 22 are pressure fitted into small locking holes 21a, 21b that are formed in positions in these members 11, 20 that are aligned with each other, joining the members 11, 20 together. These locking pins 22 are made using a relatively soft material such as an aluminum alloy, synthetic resin or the like that will shear under an impact load that is applied during a secondary collision.
When an impact load is applied during a secondary collision from the steering column 6b to the locking capsule 19 by way of the bracket 12a on the column side, these locking pins 22 shear. The locking capsule 19 then comes out in the forward direction from the locking notch 18, which allows the steering column 6b to displace in the forward direction of the steering wheel 1 that is supported by this steering column 6b via the steering shaft.
In the case of the construction illustrated in FIG. 35 to FIG. 37, the engagement section between the locking capsule 19 that is fastened to the bracket 12a on the column side and the bracket 11 on the vehicle side is located at only one location in the center section in the width direction. Therefore, tuning for disengaging this engagement section and causing the steering wheel 1 to displace stably in the forward direction during a secondary collision becomes simple.
However, in the conventional construction, that shape of the bracket 11 on the vehicle side is special, so the construction of connecting and fastening this bracket 11a on the vehicle side to the vehicle body becomes complex, and the assembly height becomes high, therefore there is a problem in that design freedom of the steering apparatus is lost. Moreover, the number of parts increases, the work for processing parts, managing parts and assembling parts becomes troublesome, and the costs increase. Furthermore, the assembly height, for example, the distance from the center of the steering column 6b to the installation surface on the vehicle side becomes large, and there is a disadvantage in that performing design in order that the steering column 6b does not interfere with the knees of the driver becomes difficult. Furthermore, construction for preventing the steering column 6a from dropping excessively together with the steering wheel 1 when the locking capsule has completely broken away from the bracket 11 on the vehicle side after a secondary collision is not considered.
Furthermore, in the case of the conventional construction illustrated in FIG. 35 to FIG. 37, reducing the load (break away load) required in order for the locking capsule 19 that is fastened to the bracket 12a on the column side to break away from the locking notch 18 that is formed in the bracket 11 on the vehicle side during a secondary collision is not particularly taken into consideration. For example, the inside edges of the locking notch 18 that is formed in the bracket 11 on the vehicle side and the edges on both the left and right sides of the locking capsule 19 directly face each other. During a secondary collision, there is friction between the inside edges of the locking notch 18 and the edges on both the left and right sides of the locking capsule 19 while the locking capsule 19 comes out in the forward direction from the locking notch 18. Therefore, in order for the locking capsule 19 to come out smoothly in the forward direction from the locking notch 18 in order to lessen the impact that is applied to the body of the driver during a secondary collision, it is necessary to keep the friction force acting between the inside edges of the locking notch 18 and the edges on both the left and right sides of the locking capsule 19 low.
On the other hand, often in order to maintain necessary strength and rigidity, the bracket 11 on the vehicle side is made by punching and bending metal plate such as carbon steel plate using a press. In regards to the inside edges of the locking notch 18, fractured surfaces that occur while forming the locking notch by punching remain. The surface roughness of the fractured surfaces is large and thus friction resistance with opposing surfaces becomes large, which is disadvantageous from the aspect of trying to lower and stabilize the force required for the locking capsule 19 to come out in the forward direction from the locking notch 18 during a secondary collision.
Moreover, in regards to the locking capsule 19, in order to sufficiently maintain reliability and durability of the connecting section between the bracket 11 on the vehicle side and the bracket 12a on the column side, often the locking capsule 19 is made of a metal material such as a ferrous metal like mild steel or an aluminum alloy. By selecting the material for each part in this way, friction occurs between metals of the bracket 11 on the vehicle side and the locking capsule 19, including the friction between inside edges of the locking notch 18 and the edges on both the left and right sides of the locking capsule 19.
The friction coefficient in areas of friction between metal materials is comparatively large. Therefore, depending on the conditions of the secondary collision, in conditions where large contact pressure is applied to the area of friction between the locking capsule 19 and the locking notch 18, the load required for the locking capsule 19 to come out in the forward direction from the locking notch 18 increases a little. Moreover, when the locking capsule 19 is made of a material such as synthetic resin or a light metal alloy that is softer than the carbon steel plate of the bracket 11 on the vehicle side, there is a possibility that the inside edges of the locking notch 18, having exposed fracture surface with large surface roughness, will bite into the side surfaces of the locking capsule 19. In such a case as well, the load required for the locking capsule 19 to come out in the forward direction from the locking notch 18 increases a little. Particularly, when a diagonal force in the forward direction is applied to the locking capsule in a collision accident, large contact pressure is applied at the area of friction between the locking capsule 19 and the locking notch 18. As a result, the break away load required for the locking capsule 19 to come out in the forward direction from the locking notch 18 becomes large, and this situation in which the break away load becomes large is not desirable from the aspect of protecting the driver.
Furthermore, in the case of the construction illustrated in FIG. 31 to FIG. 34, in a tilt/telescopic steering apparatus having both a tilting mechanism for adjusting the up/down position of the steering wheel 1 and a telescopic mechanism for adjusting the forward/backward position, the impact load that is transmitted from the steering wheel 1 to the steering column 6a by way of the steering shaft 5a during a secondary collision is input to the bracket 12 on the column side by way of supported plate sections 32 of a bracket on the displacement side that is formed in part of the steering column 6a and an adjustment rod 37 that is inserted though long holes in the up/down direction in the support plate sections 34 of the bracket 12 on the column side. In other words, during a secondary collision, this adjustment rod 37 presses strongly against the inside edges on the front side of the long holes 35 in the up/down direction. As a result, a moment in the clockwise direction of FIG. 33 and FIG. 34 is suddenly applied to the bracket 12 on the column side with the adjustment rod 37 as the point where the force is applied (input point) and the connection section between the bracket 12 on the column side and the bolt that connects this to the bracket on the vehicle side as the fulcrum. Due to this kind of moment, the edge on the front end of the top surface of the bracket 12 on the column side is strongly pressed against the bottom surface of the bracket on the vehicle side. As a result, a large friction force acts in this area, and the break away load required for coming out from the bracket on the vehicle side increases and displacement becomes unstable. Such a situation is also undesirable from the aspect of protecting the driver.
The contact pressure that is applied at the area of contact between the bracket 12 on the column side and the bracket on the vehicle side becomes larger the larger this moment is, and this moment becomes larger, the larger the distance is between the connection section, which is the fulcrum, and the input section of the break away load. This input section is where the inside edges of the long holes in the up/down direction come in contact with the outer circumferential surface of the adjustment rod 37, and this contact area normally exists further below the main section of the steering column 6a. Therefore, the distance between the connecting section and the input section becomes large, the moment becomes large and the contact pressure at the area of contact becomes high, so reducing and stabilizing the breakaway load is difficult.
It is not presumed that the conventional construction illustrated in FIG. 35 to FIG. 37 is applied to a tilt/telescopic type steering apparatus, however, when this construction is applied to a tilt/telescopic type steering apparatus, similar problems occur. However, in the case of using a locking capsule 19 in which locking grooves 20 are formed on the surfaces on the left and right sides such as illustrated in FIG. 35 to FIG. 37, the bottom surface of the bracket 11 on the vehicle side and the top surface of the bracket 12a on the column side are sufficiently separated, so even though a moment such as described above is applied to the bracket 12a on the column side during a secondary collision, the top surface of the bracket 12a on the column side will not come in contact with the bottom surface of the bracket on the vehicle side.
Particularly, when the locking capsule 19 is made of a material such as a light alloy or synthetic resin that is softer than the steel plate of the bracket 11 on the vehicle side, an increase or variation in the break away load due to the situation as described above is suppressed to a certain extent. This is because, part of the locking capsule 19 that is strongly pressed against the bottom surface of the bracket 11 on the vehicle side by the moment described above plastically deforms, causing the contact surface area to expand and the contact pressure at that point to become lower, and it is difficult for this part to bite into the opposing surfaces. As a result, as the locking capsule 19 moves in the forward direction, it becomes difficult for the top surface of the bottom plate section that defines the bottom sides of the locking grooves 20 of the locking capsule 19 to bite into the bottom surface of the bracket 11 on the vehicle side, and it becomes easier to keep the absolute value of the break away load and variations in the load low.
However, even in the case where the locking capsule 19 is made of a light alloy or synthetic resin, depending on the conditions, there is a possibility that the locking capsule 19 will be affected by the moment described above and it will not always be possible to sufficiently lower the absolute value of the break away load and variations in the load. Moreover, when the locking capsule 19 is made of a ferrous alloy for the reason of maintaining strength and rigidity, due to the same cause, there is a possibility that the absolute value of the break away load or variations in the load will become large.
JP01-69075(U) discloses construction wherein a bracket is welded and fastened to the top surface of the steering column, and during a secondary collision, there is impact between the edge on the front end of this bracket and part of the edge on the rear end of the bracket on the column side. With the construction disclosed in this document, during a secondary collision, the moment applied to the bracket on the column side is kept low, and the break away load required for the bracket on the column side to come out in the forward direction from the bracket on the vehicle side is kept low. However, in the construction disclosed in JP01-69075(U), as in the construction illustrated in FIG. 32 to FIG. 34, the bracket on the column side is supported at two locations on the left and right by the bracket on the vehicle side, so performing tuning in order to stabilize forward displacement of the steering wheel 1 requires time and trouble. Moreover, this construction does not make it possible to prevent the steering wheel 1 from dropping excessively after a secondary collision.
Of the related literature disclosing technology related to a steering column support apparatus, JP2000-6821(A) discloses construction wherein, in order to lessen the impact applied to the body of the driver that collides with the steering wheel during a secondary collision, an energy absorbing member that plastically deforms as the steering wheel and steering column displace in the forward direction is used. Moreover, in JP2007-69821(A) and JP2008-100597(A), construction is disclosed wherein, in order to increase the holding force for keeping the steering wheel in an adjusted position, a plurality of overlapping friction plates are used to increase the friction surface area. However, none of these documents discloses technology for keeping the load required for the locking capsule, which is supported by the steering column, to come out in the forward direction from the locking notch, which is formed in the bracket on the vehicle side, low.